Nonaqueous electrolytic solution containing magnesium ions, and electrochemical device using the same

Abstract

A nonaqueous electrolytic solution containing magnesium ions which shows excellent electrochemical characteristics and which can be manufactured in a general manufacturing environment such as a dry room, and an electrochemical device using the same are provided. A Mg battery has a positive-electrode can 1 , a positive-electrode pellet 2 made of a positive-electrode active material or the like, a positive electrode 11 composed of a metallic net supporting body 3 , a negative-electrode cup 4 , a negative electrode 12 made of a negative-electrode active material 5 , and a separator 6 impregnated with an electrolytic solution 7 and disposed between the positive-electrode pellet and the negative-electrode active material. Metal Mg, an alkyl trifluoromethanesulfonate, a quaternary ammonium salt or/and a 1,3-alkylmethylimidazolium salt, more preferably, an aluminum halide are added to an ether system organic solvent and are then heated, and thereafter, more preferably, a trifluoroborane-ether complex salt is added thereto, thereby preparing the electrolytic solution. By adopting a structure that copper contacts the positive-electrode active material, the electrochemical device can be given a large discharge capacity.

The invention claimed is: 
     
       1. A nonaqueous electrolytic solution comprising magnesium ions dissolved in an ether system organic solvent in which at least one of metal magnesium, alkyl trifluoromethanesulfonate having a general formula RCF 3 SO 3 , a quaternary ammonium salt having a general formula R 1 R 2 R 3 R 4 N + Z −  and a 1,3-alkyl methylimidazolium salt having a general formula R(C 3 H 3 N 2 )CH 3 ] + X −  are added to the ether system organic solvent;
 wherein in the general formula RCF 3 SO 3 , R is a methyl group or an ethyl group; 
 wherein in the general formula R 1 R 2 R 3 R 4 N + Z − , each of R 1 , R 2 , R 3 , and R 4  is an alkyl group or an aryl group, and Z −  is any one of a chloride ion (Cl − ), a bromide ion (Br − ), an iodine ion (I − ), an acetic acid ion (CH 3 COO − ), a perchloric acid ion (ClO 4   − ), a tetrafluoroboric acid ion (BF 4   − ), a hexafluorophosphoric acid ion (PF 6   − ), a hexafluoroarsenic acid ion (AsF 6   − ), a perfluoroalkylsulfonic acid ion (Rf1SO 3   − ) where Rf1 is a perfluoroalkyl group, and a perfluoroalkylsulfonyl imide ion ((Rf2SO 2 ) 2 N − ) where Rf2 is a perfluoroalkyl group; and 
 wherein in the general formula [R(C 3 H 3 N 2 )CH 3 ] + X − , R is a methyl group, an ethyl group or a butyl group, and X −  is any one of a tetrafluoroboric acid ion (BF 4   − ) and a bis(trifluoromethanesulfonyl)imide ion ((SO 2 CF 3 ) 2 N − ); 
 wherein an aluminum halide having a general formula AlY 3  is added to the ether system organic solvent, wherein in the general formula AlY 3 , Y is any one of chlorine (Cl), bromine (Br), and iodine (I). 
 
     
     
       2. The nonaqueous electrolytic solution according to  claim 1 , wherein the aluminum halide is an aluminum chloride, and the aluminum halide is added at a ratio of 1.0 mol or less per 1.0 mol of metal magnesium. 
     
     
       3. The nonaqueous electrolytic solution according to  claim 1 , wherein at least one type of trifluoroborane-ether complex salt (BF 3 (ether)) selected from the group consisting of a trifluoroborane-dimethyl ether complex salt, a trifluoroborane-ethyl methyl ether complex salt, a trifluoroborane-diethyl ether complex salt, a trifluoroborane-n-dibutyl ether complex salt, and a trifluoroborane-tetrahydrofuran complex salt is added. 
     
     
       4. The nonaqueous electrolytic solution according to  claim 3 , wherein the trifluoroborane-ether complex salt is added at a ratio of 4.0 mol or less per 1.0 mol of the metal magnesium. 
     
     
       5. The nonaqueous electrolytic solution according to  claim 1 , wherein the alkyl trifluoromethanesulfonate is at least one type selected from the group consisting of a methyl trifluoromethanesulfonate and an ethyl trifluoromethanesulfonate, and the alkyl trifluoromethanesulfonate is added at a ratio of equal to or more than 0.8 mol and equal to or less than 1.2 mol per 1.0 mol of the metal magnesium. 
     
     
       6. The nonaqueous electrolytic solution according to  claim 1 , wherein the quaternary ammonium salt is at least one type selected from the group consisting of trifluoromethanesulfonic acid tetrabutylammonium, trifluoromethanesulfonic acid tributylmethylammonium, trifluoromethanesulfonic acid triethylmethylammonium, tetrafluoroboric acid tetrabutylammonium, tetrafluoroboric acid tributylmethylammonium, tetrafluoroboric acid triethylmethylammonium, tetrabutylammoniumbis(trifluoromethanesulfonyl)imide, tributylmethylammoniumbis(trifluoromethanesulfonyl)imide, and triethylmethylammoniumbis(trifluoromethanesulfonyl)imide, and the 1,3-alkylmethylimidazolium salt is at least one kind selected from the group consisting of a 1,3-dimethylimidazoliumtetrafluoroborate, a 1-ethyl-3-methylimidazoliumtetrafluoroborate, a 1-butyl-3-methylimidazoliumtetrafluoroborate, 1,3-dimethylimidazoliumbis(trifluoromethanesulfonyl)imide, 1-ethyl-3-methylimidazoliumbis (trifluoromethanesulfonyl)imide, and 1-butyl-3-methylimidazoliumbis(trifluoromethanesulfonyl)imide. 
     
     
       7. The nonaqueous electrolytic solution according to  claim 1 , wherein any one of the quaternary ammonium salt or the 1,3-alkylmethylimidazolium salt is added at the ratio of equal to or more than 1.0 mol and equal to or less than 2.0 mol per 1.0 mol of the metal magnesium, or the quaternary ammonium salt and the 1,3-alkylmethylimidazolium salt are added at the ratio of equal to or more than 1.0 mol and equal to or less than 2.0 mol in total per 1.0 mol of the metal magnesium. 
     
     
       8. The nonaqueous electrolytic solution according to  claim 1 , wherein the ether system organic solvent is 1,2-dimethoxyethane. 
     
     
       9. The nonaqueous electrolytic solution according to  claim 1 , wherein the metal magnesium is added at the ratio of equal to or more than 0.25 mol/l and equal to or less than 1.0 mol/l to the ether system organic solvent. 
     
     
       10. An electrochemical device, comprising:
 a first electrode; 
 a second electrode; and 
 a nonaqueous electrolytic solution, the nonaqueous electrolyte solution including magnesium ions dissolved in an ether system organic solvent in which at least one of metal magnesium, alkyl trifluoromethanesulfonate having a general formula RCF 3 SO 3 , a quaternary ammonium salt having a general formula R 1 R 2 R 3 R 4 N + Z −  and a 1,3-alkyl methylimidazolium salt having a general formula R(C 3 H 3 N 2 )CH 3 ] +X   −  are added to the ether system organic solvent; 
 wherein in the general formula RCF 3 SO 3 , R is a methyl group or an ethyl group; 
 wherein in the general formula R 1 R 2 R 3 R 4 N + Z − , each of R 1 , R 2 , R 3 , and R 4  is an alkyl group or an aryl group, and Z −  is any one of a chloride ion (Cl − ), a bromide ion (Br − ), an iodine ion (I − ), an acetic acid ion (CH 3 COO − ), a perchloric acid ion (ClO 4   − ), a tetrafluoroboric acid ion (BF 4   − ), a hexafluorophosphoric acid ion (PF 6   − ), a hexafluoroarsenic acid ion (AsF 6   − ), a perfluoroalkylsulfonic acid ion (Rf1SO 3   − ) where Rf1 is a perfluoroalkyl group, and a perfluoroalkylsulfonyl imide ion ((Rf2SO 2   − ) 2 N − ) where Rf2 is a perfluoroalkyl group; 
 wherein in the general formula [R(C 3 H 3 N 2 )CH 3 ] + X − , R is a methyl group, an ethyl group or a butyl group, and X −  is any one of a tetrafluoroboric acid ion (BF 4   − ) and a bis(trifluoromethanesulfonyl)imide ion ((SO 2 CF 3 ) 2 N − ); and 
 wherein an active material of the second electrode is oxidized to generate magnesium ions. 
 
     
     
       11. The electrochemical device according to  claim 10 , wherein the active material of the first electrode is made from any one of a compound which reacts with the magnesium ion and a compound which occludes the magnesium ion, and wherein the active material of the second electrode is made from any one of a metal single body of magnesium and an alloy containing magnesium. 
     
     
       12. The electrochemical device according to  claim 10 , wherein the first electrode is a positive electrode including a positive-electrode active material made from a graphite fluoride and a positive-electrode mixture containing copper, and the second electrode is a negative electrode containing any one of a magnesium metal and a magnesium alloy as a negative-electrode active material. 
     
     
       13. The electrochemical device according to  claim 10 , wherein the first electrode is a positive electrode including a positive-electrode mixture containing a positive-electrode active material made from a graphite fluoride, the second electrode is a negative electrode containing any one of a magnesium metal and a magnesium alloy as the negative-electrode active material, and the electrochemical device has at least one of a positive-electrode power collecting body made of at least one of a conductive material covered with copper and copper; and a positive-electrode can having an inner surface covered with copper contacting therein the positive-electrode active material. 
     
     
       14. The electrochemical device according to  claim 10 , wherein the electrochemical device is configured as a battery.